Search

The paper presents the results of experimental studies of the structure and magnetoresistive properties of discontinuous multilayers [Ni80Fe20(d)/SiOx(5)]5/Substrate, x ≅ 1. The method of layer-by-layer electron-beam evaporation was used for the deposition of samples. The thickness of the magnetic layers (d) varied from 4 to 8 nm. To investigate the annealing temperature effect on magnetoresistive properties, samples were annealed at step-increasing temperatures within the Tann = 300 700 K range. It was demonstrated that an anisotropic character of magnetoresistance (positive longitudinal and negative transverse magnetoresistance) is observed for all as-deposited and annealed at 400 K samples, which are typical for single-layer structurally continuous films of the Ni80Fe20 alloy. Familiar to all field dependences (△R/Ro)(B) with an anisotropic character is a sharp change in magnetoresistance in the field range of 10+10 mT and a tendency to saturate in more vital fields. It was found that annealing the samples at a temperature of 500 K with d = 4 - 5 nm leads to the transition to isotropic magnetoresistance. This is due to an increase in the size of permalloy granules to 10 nm and the formation of insulator channels with a width of 12 nm between them. The maximum values of isotropic magnetoresistance at room temperature are about 0.1%. After annealing at a temperature of 600 K, the reappearance of anisotropic magnetoresistance in structures with d = 4 nm is observed. The reason for this transition is the destruction of the structural continuity of the insulator layers and, as a result, the formation of a metal cluster throughout the structure. It is shown that an increase in the annealing temperature to 700 K does not cause a change in the nature of the magnetoresistance but only leads to a rise in its value. [ABSTRACT FROM AUTHOR]

The paper deals with the influence of d-f exchange interactions occurring in the contact zone of layers in Fe/REM oxide nanostructures on the features of their infrared absorption spectra. The time-distances, energies and force constants of vibrations of Gd-O and Yb-O atomic bonds in Fe/Gd2O3 and Fe/Yb2O3 nanostructures with significant and small values of the effective magnetic moment of REM, respectively, have been compared. It is shown that the difference between the absorption spectra of these nanostructures and the properties calculated from them indicates the presence of the influence of the d-f exchange interaction on the vibrations of the Gd-O bond and its absence for Yb-O. For the Gd-O bond, the increase in vibrational energy due to the d-f exchange interaction is 0.02-0.11 %. It is shown how the influence of the exchange interaction can be taken into account in the well-known quantum mechanical description of the anharmonicity of the oscillator vibrations by introducing an additional term in the expression for its potential energy. This approach makes it possible to show that the d-f exchange interaction also affects the value of the distance between the nuclei of Gd-O atoms. [ABSTRACT FROM AUTHOR]

The frequency characteristics of impedance, phase difference between current and voltage, hodographs, and corresponding equivalent circuits of Fe nanofilms grown in a constant magnetic field on Gd2O3 and silicate glass substrates are investigated. It is shown that with increasing magnetic field strength from 40 E to 1200 E, the morphology of Fe films changes from labyrinthine to continuous, consisting of coalesced iron islands. This complex morphology of the films is the source of the induction and capacitance components of the imaginary part of the impedance. It was found that at a frequency of 630 Hz, a consistent electrical resonance is observed in Fe films, as well as a minimum value of the total impedance. At frequencies above 104 Hz, a sharp change in the impedance components and phase difference is observed in Fe films, which is probably due to the peculiarities of the film morphology. The Nyquist hodographs were constructed and the parameters of the corresponding equivalent circuits were calculated using the ZView computer program. It is shown that both the equivalent schemes of the hodographs and the peculiarities of the frequency dependence of the impedance and phase difference components depend largely on the morphology of the films, which is determined by the elasticity of the magnetic field applied during their growth, as well as by the chemical composition of the substrates. Gd2O3 substrates affect Fe films due to the d-f exchange interaction between the unfilled f and d electron shells of the atoms that make up the Gd2O3 and Fe layers. Silicate glass has an effect due to the ions of technological impurities contained in its composition, which can act as traps for electrons passing through the Fe film. [ABSTRACT FROM AUTHOR]

The phase state, electrical conductivity and magnetoresistive properties of binary film alloys based on Fe, Co and Ni prepared by the method evaporation in high vacuum in the temperature range 100700 K have been studied. It has been shown that the fcc-phase is observed for as-deposited and annealed up to 700 K Fe0,50Ni0,50 thin films with a thickness d 10100 nm, the fcc-phase is observed. For Fe0,67Ni0,33 Fe0,50Co0,50 and Fe0,67Co0,33 thin films, the bcc-phase is fixed. It was found that the size dependences of the resistivity, temperature coefficient of resistance and magnetoresistance are realized for all structurally continuous film alloys. The character of size dependences is а like the corresponding dependences for the pure metal films. It has been shown that for Fe0,67Ni0,33, Fe0,50Co0,50 and Fe0,67Co0,33 the size dependences of both longitudinal and transverse magnetoresistance appear much weaker than for Fe0,50Ni0,50 thin alloy. For Fe0,67Ni0,33, Fe0,50Co0,50 and Fe0,67Co0,33 thin alloys, the value of both longitudinal and transverse magnetoresistance is weakly depending on the temperature. [ABSTRACT FROM AUTHOR]

The qualitative analysis of the giant magnetoresistive effect in three-layer magnetically ordered films (sandwiches) was carried out using the two-current model and the theory of dimensional effects. It is shown that in the region of small thicknesses of the covering magnetic layer the magnetoresistance of the conductor increases compared to the thickness of the base magnetic layer, while in the opposite region of thicknesses it decreases, and in the specified thickness the effect is negligible due to the presence of the shunt effect. In the case when the thickness of the covering magnetic layer of the metal is proportional to the total thickness of the base magnetic layer and the non-magnetic layer, the value of magnetoresistance reaches its maximum value due to the absence of the shunting effect. It is shown that the insignificant value of the effect is due to the shunting of the resistances of the covering and base magnetic layers. If the thickness of the covering magnetic layer of the metal is comparable to the total thickness of the main magnetic layer and the nonmagnetic layer, the value of magnetoresistance reaches its maximum value due to the absence of the shunting effect mentioned above. [ABSTRACT FROM AUTHOR]

Dimensional effects in the magnetoresistive properties of FeхСо1 – х/Сu/FeхСо1 – х three-layer magnetically ordered films obtained by layer-by-layer metal condensation followed by heat treatment in the temperature range of 300 σ 550 K were studied experimentally and theoretically using generalized Dieny formulas [1, 2]. It is shown that in the case when the cover layer thickness is much smaller (greater) than the base layer thickness, the numerical value of the magnetoresistance ratio σ is negligible due to shunting of the covering layer resistance by the resistances of the base layer and the nonmagnetic layer (shunting of the resistances of the base layer and the nonmagnetic layer by the resistance of the covering magnetic layer). If the thickness of the base and cover layers are the same, the value of σ becomes maximum due to the absence of the shunting effect. If the thickness of the non-magnetic layer increases, provided that the thicknesses of the base and magnetic layers of the metal do not change, the magnetoresistance ratio monotonically decreases with increasing spacer thickness. [ABSTRACT FROM AUTHOR]

The influence of the magnetic and insulator layer thickness on the crystal structure and magnetoresistive properties of [Fe/SiO]n discontinuous multilayers has been studied. The results indicate that the decreasing of Fe layer thickness within the range from 10 to 3 nm leads to the transition of microstructure of the samples from nanocrystalline to amorphous. For all investigated systems in an as-deposited state, the isotropic nature of the field dependences of magnetoresistance is observed. For samples with layer thickness dFe = 4–6 nm and dSiO = 5 nm, the transition to isotropic MR occurs after annealing to 400 K. However, for samples with Fe layer thickness of 7–10 nm, such transition is not observed regardless of the effective thickness of insulator layer and annealing temperature. [ABSTRACT FROM AUTHOR]

The paper presents experimental results concerning the structural-phase state, diffusion processes and magnetoresistive properties of three-layer films Сo(1 – x)Crx/Cu/Co/substrate (S) with Cr concentration in the upper layer up to 30 at. %. It is shown that the phase composition of both as-deposited and thermostabilized at the temperature of 700 K film samples with the layer thickness of 1÷30 nm corresponds to α(Co), f.c.c.(Cu) and α(Сo1 – xCrx). Studies of diffusion processes have shown that in the systems Сo(1 –x )Crx/Cu/Co/S the individuality of the layers is largely preserved both in the as-deposited state and after annealing at Tа = 700 K with the penetration of Cr atoms through the Cu layer. It was found that for as-deposited and annealed at temperatures of 400 and 550 K films Сo(1 – x)Crx/Cu/Co/S with cCr < 30 at. % in the upper layer, dF = 20÷30 nm and dN = 3÷15 nm there is an atypical character of the behavior of the field dependences of the magnetoresistance is due to the different values of the spin asymmetry coefficients of the ferromagnetic layers α [ABSTRACT FROM AUTHOR]

Copyright of Journal of Nano- & Electronic Physics is the property of Sumy State University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Progress in Physics of Metals / Uspehi Fiziki Metallov is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Metallophysics & Advanced Technologies / Metallofizika i Novejsie Tehnologii is the property of G.V. Kurdyumov Institute for Metal Physics, N.A.S.U and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The paper presents results of experimental studies of crystal structure and electrical resistivity in the three-layer Co / Ag / Fe and Co / Cu / Fe nanocrystalline films and. It has been shown that all the samples, annealed at 700 K with dCu,Ag > 5 nm, are three-phase (FCC-Co, FCC-Ag, FCC-Cu, respectively, and BCC-Fe). The dependence of the three-layer films resistivity on the layer thickness has been obtained experimentally. It has been detected that the above-mentioned dependence is nonmonotonic, which is conditioned by the diffuse nature of the interaction of electrons with interfaces of the conductor. [ABSTRACT FROM AUTHOR]